The present invention relates to a gate driver having level shift circuit for driving the gate of a power semiconductor device.
Many low voltage electronic circuits, e.g., MOSFET devices, are used to drive high voltage switching transistors, e.g., power MOSFETs, insulated gate bipolar transistor devices (IGBTs), gate controlled thyristors, and the like. A power semiconductor switch or device is switched from a nonconducting state to a conducting state by raising the gate-source voltage from below to above a threshold voltage. As used herein, the term “power device” or “power semiconductor device” refers to any power MOSFET, IGBT, thyristor, or the like.
One or more low voltage transistors, coupled to an output node of the gate driver, apply appropriate voltages to the gate or control terminal of the power device to turn on or turn off the power device. When the power device is an N-channel metal oxide semiconductor field effect transistor (NMOSFET), the device is turned on by applying a high voltage to the gate of the power switch and turned off by applying a low voltage to the gate. In contrast, if the power device is a P-channel metal oxide semiconductor field effect transistor (PMOSFET), the device is turned on by applying a low voltage to the gate of the power switch and turned off by applying a high voltage to the gate. Unless otherwise explained, power devices, as used herein, refer to in N type devices for ease of illustration.
Generally, a gate driver includes a level shifting circuit for shifting the potential of a small control signal to a higher voltage level that is more suitable for turning on the power device. The gate driver may be packaged as a single device having a high side portion and a low side portion, where the high side is used to turn on or off a high side switch or transistor of the power device and the low side is used to turn on or off a low side switch or transistor of the power device. The high side switch has a drain coupled to a high voltage source, e.g., 1000 volts, while the low side switch has a drain coupled to a lower voltage source, e.g., a source of the high side switch.